Shoes were originally intended to protect feet from external impact or foreign matter. However, users often add special functions to shoes. Alternatively, in many cases, shoes have special functions from the manufacturing stage. For example, climbers attach climbing irons to shoes to prevent slipping, and wheeled shoes were once widely prevalent.
However, apparatuses, such as climbing irons, for providing special functions to shoes have problems in that the apparatuses are not easy to attach or are not robust even though attached. Furthermore, shoes having a predetermined function from the manufacturing stage are inefficient in that it is difficult to provide a different function, other than the function, to the shoes.